docs: def dtype(self, byte_order='='):
          '''
          Return the numpy dtype of the in-memory representation of the
          data.  (If there are no list properties, and the PLY format is
          binary, then this also accurately describes the on-disk
          representation of the element.)
  
          '''
          return _np.dtype([(prop.name, prop.dtype(byte_order))
                            for prop in self.properties])